Spent coffee grounds (SCG) are usually disposed as common garbage, without specific reuse strategies
implemented so far. Due to its recognised richness in bioactive compounds, the effect of SCG on lettuce’s
macro- and micro-elements was assessed to define its effectiveness for agro industrial reuse. A
greenhouse pot experiment was conducted with different amounts of fresh and composted spent coffee,
and potassium, magnesium, phosphorous, calcium, sodium, iron, manganese, zinc and copper were
analysed. A progressive decrease on all lettuce mineral elements was verified with the increase of fresh
spent coffee, except for potassium. In opposition, an increment of lettuce’s essential macro-elements was
verified when low amounts of composted spent coffee were applied (5%, v/v), increasing potassium
content by 40%, manganese by 30%, magnesium by 20%, and sodium by 10%, of nutritional relevance This
practical approach offers an alternative reuse for this by-product, extendable to other crops, providing
value-added vegetable products.
